Scientists have developed a groundbreaking atom interferometer capable of amplifying faint signals by 1,000 times — making it 50 times more sensitive than previous models.
This tool, which uses laser pulses to manipulate atoms, corrects for imperfections that have long hindered precision. With this innovation, researchers hope to detect ultra-weak forces from dark matter, dark energy, and gravitational waves.
Unlocking the Secrets of Dark Matter
If dark matter exists, its interactions with ordinary matter are so weak that even the most advanced instruments struggle to detect them.
Now, physicists at Northwestern University have developed a groundbreaking tool that amplifies extremely faint signals by 1,000 times — a 50-fold improvement over previous technology.
This device, known as an atom interferometer, uses light to manipulate atoms and measure incredibly small forces. Unlike earlier versions, which suffer from imperfections in the light itself, this new interferometer self-corrects for these flaws, achieving unprecedented precision.
A Game Changer for Dark Matter and More
By making previously undetectable signals measurable, this breakthrough could aid scientists in their search for ultra-weak forces linked to elusive phenomena such as dark matter, dark energy, and gravitational waves at unexplored frequencies.
“Dark matter is somewhat of an embarrassing problem,” said Northwestern’s Timothy L. Kovachy, who led the work, which was published in Physical Review Letters. “It’s a weird dichotomy because the ordinary matter that we encounter in everyday life, we understand extremely well. But that only makes up 15% of the matter in the universe. We don’t know the nature of the rest, which makes up most of the matter in the universe. So, it’s just a big incompleteness. Atom interferometers could potentially have a big impact in searching for this kind of dark matter.”
Kovachy is an assistant professor of physics and astronomy at Northwestern’s Weinberg College of Arts and Sciences and a member of the Center for Fundamental Physics.
What Is an Atom Interferometer?
Invented in 1991, atom interferometers take advantage of superposition, a fundamental principle in quantum mechanics that a particle can exist in multiple states simultaneously. In this case, an atom behaves like a wave that exists along two paths at once. In an atom interferometer, lasers split a wave-like atom into two waves, send those waves on two different paths, and then recombine them.
When the waves recombine, they create a pattern, which is like a fingerprint that reveals forces acting on the atoms. By studying this pattern, scientists can measure tiny, invisible forces and accelerations.
“Atom interferometers are really good at measuring small oscillations in distances,” Kovachy said. “We don’t know how strong dark matter is, so we want our instruments to be as sensitive as they can be. Because we haven’t ‘seen’ dark matter yet, we know its effects must be pretty weak.”
Challenges of Current Instruments
When working with waves this tiny, however, it doesn’t take much to disrupt the entire experiment. Even the tiniest imperfection can lead to errors in the interference pattern. A single photon, for example, can derail the wave-like atom’s path — kicking it off-course with a velocity of one centimeter per second.
“Photons can’t carry that much momentum, but atoms also don’t have that much mass,” Kovachy explained. “If we lose one atom, that doesn’t seem like the end of the world. But if we apply many laser pulses of light to boost the atom interferometer’s ability to amplify small signals, those errors will compound. And they will compound fast. In practice, we saw that after about 10 pulses, the signal was just gone.”
A ‘Self-Correcting’ System for Greater Precisionsystem
To overcome this challenge, Kovachy and his team developed a new technique to carefully orchestrate the sequence of laser pulses. Leveraging machine-learning approaches, the method “self-corrects” for the imperfections in individual pulses of light. By controlling the waveforms of laser pulses, the researchers reduced the overall effect of errors caused by imperfections in the experimental setup.
After testing the model in simulations, Kovachy’s team built the experiment in the lab. The experiments verified the signal was amplified by 1,000 times.
A New Era for Atom Interferometry
“Before, we could only do 10 laser pulses; now we can do 500,” Kovachy said. “This could be game-changing for many applications. The atom interferometer as an entire entity ‘self-corrects’ for the imperfections in each laser pulse. We can’t make each laser pulse perfect, but we can optimize the global sequence of pulses to correct for imperfections in each one. That could allow us to unlock the full potential of atom interferometry.”
Reference: “Robust Quantum Control via Multipath Interference for Thousandfold Phase Amplification in a Resonant Atom Interferometer” by Yiping Wang, Jonah Glick, Tejas Deshpande, Kenneth DeRose, Sharika Saraf, Natasha Sachdeva, Kefeng Jiang, Zilin Chen and Tim Kovachy, 11 December 2024, Physical Review Letters.
DOI: 10.1103/PhysRevLett.133.243403
